Module 2, Chapter 8

acetabular labrum

A circular rim of fibrocartilage; increases the depth of the acetabulum. Hip joint dislocations are rare because the articular surfaces fit tightly together. The labrum's diameter is less than that of the head of the femur, however.

dislocation

A dislocation is also known as a luxation. It occurs when bones are forced out of alignment and usually is involved with a sprain. There is inflammation and difficulty in moving the joint. Common causes of dislocations include falling and contact sports. The most commonly dislocated joints are those of the jaw, fingers, thumbs, and shoulders. Dislocations, like fractures, must be reduced. This means the ends of the bones must be returned to their proper positions by a physician. Partial dislocation of a joint is called subluxation. Because an initial dislocation stretches a joints capsule as well as its ligaments, repeat dislocations of the same joint often occur. The joint then has poor reinforcement because the capsule has become loose

articular cavity

A potential space containing a small amount of synovial fluid.

reinforcing ligaments

Band-like accessory structures that reinforce and strengthen synovial joints. They are primarily capsular ligaments (actually, thicker parts of the fibrous layer). They are distinct from and remain outside the capsule (extracapsular ligaments) or remain deep to it (intracapsular ligaments). The intracapsular ligaments do not actually lie within the joint cavity because they are covered with synovial membrane. The term double-jointed actually means a person's joint capsules and ligaments are looser, with more ability to stretch, than those of the average person.

flexion

Bending parts at a joint so they come closer together. It usually occurs along the sagittal plane, decreasing the angle of the joint. Examples include bending the trunk or the knee from a straight to an angled position or bending the head forward toward the chest.

bursitis

Bursitis is inflammation of the bursae, which is often caused by trauma or friction. Examples of bursitis include conditions known as water on the knee and student's elbow. If severe, common treatments include injection of anti-inflammatory drugs into the bursae or removal of excessive fluid via needle aspiration.

angular movements

Decrease or increase the angle between two bones. This can occur in any body plane and includes extension, flexion, hyper-extension, abduction, adduction, and circumduc-tion

hyperextension

Extending the parts at a joint beyond the normal range of motion, often resulting in injury because the anatomic position is exceeded.

ellipsoidal joint

Having biaxial movement that involves adduction and abduction around an anterior/posterior axis and flexion and extension around a medial/lateral axis, with oval articular surfaces. Examples include the metacarpophalangeal (knuckle) joints and wrist joints.

saddle joint

Having biaxial movement that involves flexion and extension and adduction and abduc-tion, saddle joints function around the same type of axis configurations as condylar joints. Articular surfaces are both concave and convex. An example is the carpometacarpal joints of the thumbs.

ball and socket joint

Having multiaxial movement that involves rotation, adduction, abduction, flexion, and extension. Ball-and-socket joints use vertical, anterior/posterior, and medial/lateral types of axis structures, with spherical heads in cup-like sockets. Examples include the shoulder and hip joints

plane (gliding joint)

Having nonaxial movement that involves linear gliding and flat, articular surfaces. Examples include the intercarpal joints, intertarsal joints, and the joints between vertebral articular surfaces.

hinge joint

Having uniaxial movement that involves flexion and extension along a medial/lateral axis, they have cylinders and troughs. Examples include the elbow joints and interphalangeal joints.

pivot joint

Having uniaxial movement that involves rotation around a vertical axis, they have bone and ligament sleeves as well as rounded bones (axles). Examples include the proximal radioulnar joints and the atlantoaxial joint.

Flexion and extension is allowed by the hinge-like tibiofemoral joint.

In actuality, it is a bicondylar joint, with some rotation occurring when the knee is slightly flexed or when it is extending.

nucleus pulposus

Inside the annulus fibrosis is the nucleus pulposus, a core that is softer, gelatinous, and more elastic. Intervertebral discs absorb shocks and have resiliency because of each nucleus pulposus. Thin vertebral end plates nearly cover the superior and inferior surfaces of each disc. The plates are made up of fibrocartilage and hyaline cartilage. When movement occurs, the vertebral column compresses the nucleus pulposus, displacing it in opposing directions. Gliding movements can occur while vertebral alignment remains constant.

rotation movements

Involve the turning of a bone around its long axis. This is common at the hip and shoulder joints and is the singular movement allowed between the first two cervical vertebrae. Rotation may be directed away from the midline or toward it. Examples include the thighs medial rotation and when the anterior surface of the femur moves toward the body's median plane. The oppo-site movement of medial rotation is called lateral rotation.

opposition

Involving the saddle joint between the trapezium and metacarpal I, the thumb performs opposition when you touch it to the tips of the other fingers on the same hand. Opposition allows us to grab a hammer or a glass of water. Reposition returns the thumb and fingers from opposition.

arcuate popliteal ligament

It fuses with the joint capsule. The joint capsule is reinforced posteriorly by the arcuate popliteal ligament, which has a superior arc, from the head of the fibula over the popliteus muscle.

depression

Lowering a part (moving it inferiorly). When you chew, your mandible is elevated and depressed repeatedly.

lyme disease

Lyme disease may also affect the joints and is caused by spirochete bacteria. It is transmitted by ticks that infest deer or mice. Lyme disease may cause joint (often knee) pain, arthritis, skin rash, flu-like symptoms, and impaired cognition. Untreated Lyme disease results in neurological and cardiovascular problems. It is very difficult to diagnose and usually requires a long course of antibiotics.

articular cartilage

Made up of smooth hyaline cartilage covering opposing bone surfaces. Although only 1 mm (or thinner) in thickness, they absorb compression and help to keep bone ends from being crushed.

rotation

Moving a part around its axis, either directed toward the midline or away from it. It is common at the hip, shoulder, and first two cervical vertebrae.

abduction

Moving a part away from the midline (longitudinal axis), or median plane, of the body. An example is when the arm or thigh is raised lat-erally. For the toes or fingers, it means "spreading apart." However, the lateral bending of the trunk away from the body midline (in the frontal plane) is not called abduction but lateral flexion.

retraction

Moving a part backward, which is a nonangular posterior movement in the transverse plane. For example, the mandible is retracted when you pull your jaw back after sticking it out

protraction

Moving a part forward, which is a non-angular anterior movement in the transverse plane. For example, the mandible is protracted when you stick your jaw out.

circumduction

Moving a part so its end follows a circular path, as if describing a cone in space. The distal end of a circumducting limb moves in a circle, whereas the "point" of the cone (the hip or shoul-der joint) remains nearly stationary. Circumduction actually consists of the movements of flexion, then abduction, then extension, then adduction.

adduction

Moving a part toward the midline of the body. For the toes or fingers, it is moving them toward the midline of the foot or hand.

plantar flexion

Moving the ankle so the foot moves farther from the shin, pointing the toes. This corresponds to wrist flexion.

dorisflexion

Moving the ankle so the top of the foot comes closer to the shin or moving the wrist so the back of the hand comes closer to the arm (wrist extension).

osteoarthritis

Osteoarthritis is the most common chronic form of arthritis. Degeneration of joints, via enzymatic activity, occurs due to aging in most patients. Degenerative joint dis-ease occurs more commonly in women, usually affecting the knees and other weight-bearing joints and the distal finger joints. Nearly half of all adults develop osteoarthritis by age 85, and women are more commonly affected than men. In people with osteoarthritis, more cartilage is destroyed than can be normally replaced. Poorly aligned or overused joints are most likely to develop osteoarthritis. Exposed bone tissue becomes thicker over time, forming bony osteophytes (spurs). These enlarge bone ends, restricting joint movement. Affected joints may "crunch," a condition known as crepitus. Most commonly, the joints of the cervical or lumbar spine, fingers, knuckles, knees, and hips are affected. Osteoarthritis develops slowly, is irreversible, and causes pain, joint stiffness, and inflamma-tion. Treatments include pain relievers, moderate activity, cap-saicin, and nutritional supplements. Continuous passive motion helps an injured joint to repair by improving circulation of synovial fluid. This is often performed by a machine or phys-ical therapist working with the patient.

nerves and blood vessels

Plentiful in synovial joints, sensory nerve fibers innervate the joint capsule, whereas most of the blood vessels supply the synovial membrane. Some sensory nerve fibers detect pain, but most regulate the joint's position and stretching ability. Therefore, these fibers allow the nervous system to monitor body posture and movements. Extensive capillary beds produce the blood filtrate, which is the basis of synovial fluid

elevation

Raising a part (lifting it superiorly). When you shrug your shoulders, the scapulae are elevated.

rheumatoid arthritis

Rheumatoid arthritis is an autoimmune disorder that primarily affects the small joints of the hands, causing pain, stiffness, and deformity. Rheumatoid arthritis is a chronic inflammatory disorder that usually appears between the ages of 30 and 50. It is less common than osteoarthritis and affects women three times more often than men. Initially, joint tenderness and stiff-ness are common. It usually manifests in the fingers, wrists, ankles, and feet, on a bilateral basis. Rheumatoid arthritis is marked by exacerbations and remissions, which may include anemia, muscle weakness, osteoporosis, and cardiovascular abnormalities. It is an autoimmune disease, in which the immune system attacks its own tissues. Although cause is not completely understood, it may be related to various bacteria and viruses. The synovitis (synovial membrane) of an affected joint becomes inflamed first.

extension

Straightening parts at a joint so they move farther apart. The reverse of flexion, it occurs at the same joints, also along the sagittal plane. The angle between the articulating bones is increased. This usually straightens a flexed body part, such as a limb. Examples include the straightening of a flexed elbow, neck, or knee.

tendonitis

Tendonitis is inflammation of tendon sheaths, which is usu-ally caused by excessive wear. This condition has similar symptoms to bursitis, which include pain and swelling. Treatment of tendonitis includes ice, rest, and anti-inflammatory drugs.

anterior cruciate ligament

The anterior cruciate ligament is attached to the tibia's anterior intercondylar area and passes upward, laterally, and posteriorly to attach to the femur. Its actual point of attachment is the medial side of the femur's lateral condyle. The anterior cruciate ligament prevents the tibia from sliding for-ward on the femur, controlling hyperextension of the knee. It is tight during knee extension and slightly relaxed during knee flexion

The intervertebral ligaments are as follows:

The anterior longitudinal ligament: connecting anterior surfaces of adjacent vertebral bodies The posterior longitudinal ligament: connecting posterior surfaces of adjacent vertebral bodies The ligamentum flavum: connecting the laminae of adjacent vertebrae The interspinous ligament: connecting the spinous processes of adjacent vertebrae The supraspinous ligament: interconnecting the tips of spinous processes, from C7 to the sacrum

elbow joint

The elbow joints allow only flexion and extension and are stable hinge joints that operate very smoothly. The radius and ulna bones both articulate inside each elbow joint with the condyles of the humerus. The hinge of the elbow joint is formed by the tight gripping of the trochlea by the trochlear notch of the ulna. Joint stabilization is provided by this structure. The articular capsule is relatively loose. It extends inferiorly from the humerus to the radius and ulna and to the annular ligament that surrounds the head of the radius.

hip joints

The hip joints are also known as the coxal joints. They are ball-and-socket joints with less range than those of the shoulder. Although widely ranging movements are possible, they are limited by the deep hip sockets and strong ligaments. Each hip joint is formed by the articulation of the femurs spherical head with the hip bone's acetabulum and its deeply cupped position

iliofemoral ligament,

The iliofemoral ligament lies anteriorly and is very strong, with a V-shape. reinforces the articular capsule of the hip with the pubofemoral ligament and the ischiofemoral ligament. All three ligaments have an arrangement that causes a screw-like turning motion of the femur head into the acetabulum when a person stands up straight. They provide increased joint stability.

knee joint

The knee joint has a single joint cavity yet is the most complex joint in the body. It is actually made up of an intermediate joint between the patella and lower femur and lateral and medial joints collectively known as the tibiofemoral joints. These joints lie between the femoral condyles above and the semilunar cartilages (C-shaped menisci) of the tibia below.

oblique popliteal ligament,

The posterior aspect of the knee joint is partially stabilized by the oblique popliteal ligament, which is part of the tendon of the semimembranosus muscle. It fuses with the joint capsule.

posterior cruciate ligament

The posterior cruciate ligament has more strength and is attached to the tibia's posterior intercondylar area. This ligament passes superiorly, medially, and anteriorly, attaching to the lateral side of the medial condyle of the femur. It prevents forward sliding of the femur or backward displacement of the tibia.

ost of the stability of the shoulder joint comes from muscle tendons that cross the joint.

The primary stabilizing structure is the tendon of the long head of the arm's biceps brachii muscle. This tendon secures the head of the humerus against the glenoid cavity. It is attached to the glenoid labrum's superior margin and travels through the shoulder joint cavity. It then continues within the intertubercular sulcus of the humerus.

pubofemoral ligament

The pubofemoral ligament is a triangular thickening of the inferior area of the capsule. reinforces the articular capsule of the hip with the iliofemoral ligament and the ischiofemoral ligament. All three ligaments have an arrangement that causes a screw-like turning motion of the femur head into the acetabulum when a person stands up straight. They provide increased joint stability.

semilunar cartilages

The semilunar cartilages deepen the tibial articular surfaces, which are otherwise shallow. They absorb shock to the knee joint and also prevent horizontal rocking of the femur on the tibia. Unfortunately, the semilunar cartilages are often completely torn because they are only attached at their outer margins.

synovial fluid

The slippery liquid found in all free spaces inside the joint capsule is mostly synthesized by filtration from blood in the synovial membrane capillaries. similar to egg whites, with a thick consistency, because of hyaluronic acid that is secreted by synovial membrane cells. When the joint is in motion, the fluid thins and becomes less viscous. Synovial fluid is also found inside articular cartilages as a slippery film. It bears weight, reducing friction between cartilages. Without it, joint surfaces would be destroyed from use. When a joint is compressed, the fluid is forced out of the cartilages. As joint pressure is relieved, it flows back into the articular cartilages quickly. This process is called weeping lubrication, which also provides nourishment to the cells of the joint cartilage. Synovial fluid also has phagocytic cells that patrol the joint cavity for microbes and cell debris.

Synovial joints

These joints allow free movement (diarthrotic) and are more complex than other types of joints. Synovial joints have outer layers of ligaments (joint capsules) and inner linings of synovial membrane that secrete synovial fluid, which lubricates these joints. Some synovial joints have shock-absorbing fibrocartilage pads called menisci. They may also have fluid-filled sacs (bursae), commonly located between tendons and underlying bony prominences such as in the knee or elbow. The synovial fluid lubricating these joints allows for great freedom of movement. All syno-vial joints are freely moving diarthroses. Most joints of the body, and nearly all joints of the limbs, are synovial joints. Fat pads are localized adipose tissue masses that are covered by a synovial membrane layer.

The knee joint is the only articulation that has a cav-ity partially enclosed by a capsule

This capsule is thin and present only on the posterior aspects and sides of the knee. It covers most of the femoral and tibial condyles. It is absent anteriorly, and here there are three broad ligaments running from the patella to the tibia below, the patellar, medial, and lateral patellar retinacula ligaments. They merge with the articular capsule on each side. Two of them (the patellar ligament and the lateral patellar retinacula) are continuations of the tendon from the quadriceps muscle in the anterior thigh. The patellar ligament is used to test the knee-jerk reflex.

articular capsule

This two-layered structure that encloses the joint cavity has a tough outer fibrous layer made up of dense irregular connective tissue, which is continuous with the periostea of articulating bones. The capsule strengthens the joint and ensures the bones are not pulled apart. Each joint capsule's inner layer is known as the synovial membrane.

annulus fibrosis

Throughout most of the spine, each intervertebral disc has a tough outer layer of fibrocartilage known as the:

eversion

Turning the foot so the plantar surface (sole) faces laterally.

inversion

Turning the foot so the plantar surface faces medially

supination

Turning the hand so that the palm is upward, facing anteriorly. The forearm is rotated laterally In the anatomical position, the hand is supinated while the radius and ulnae are parallel.

pronation

Turning the hand so the palm is down-ward, facing posteriorly. The forearm is rotated medially moving the distal end of the radius across the ulna, forming an X between the two bones. The forearm remains in this position when a person is standing but relaxed. Pronation is not as strong a movement as supination.

gliding movements

When a flat (or nearly flat) bond surface slips over or glides over another in a side-to-side or back-and-forth motion. There is no major rotation or angulation. Examples include the movement of the intertarsal and intercarpal joints and between the flat articular vertebral processes.

joints

also referred to as articulations, act as junctions between bones and vary widely in structure and function. They are classified both as to how they move and according to the types of tissue that binds bones together at the joint. The two primary functions of joints are to hold the skele-ton together (which offers a certain amount of protection) and to make the skeleton mobile. However, they are the weakest components of the skeleton. They resist tearing, crushing, and other forces that are able to force them out of alignmen

shoulder separation

an injury involving partial or complete dislocation of the acromioclavicular joint

Basically, there are three general types of movements:

angular, gliding, and rotation:

The six characteristics of synovial joints are as follows:

articular cartilage, articular cavity, articular capsule, synovial fluid, reinforcing ligaments, and nerves and blood vessels.

intervertebral joints

between superior and inferior articular processes of adjacent vertebrae in the spine; These are gliding joints, allowing small movements such as flexion and rotation of the spinal column. However, only slight gliding occurs between adjacent vertebrae. Therefore, the vertebrae are separated and cushioned by intervertebral discs, which are pads of fibrocartilage

arthroscopic surgery

damaged cartilage is usually surgically removed via: _______ An arthroscope is used, which is very small, containing a miniscule lens and fiber-optic light source. The surgeon can look inside the joint to determine surgical options. Ligaments can be repaired or frag-ments of cartilage removed through one or several small slits. This reduces tissue damage and scarring. If only part of the meniscus is removed, mobility is not severely impaired, but the joint becomes much less stable

bursae

flat fibrous sacs that have synovial membranes lining them. They contain a thin film of synovial fluid and are located where bones, ligaments, muscles, skin, or tendons rub together.

diarthrotic

freely movable aka synovial

cartilaginous joints

include those that separate the vertebrae. Each intervertebral disc is an example of a cartilaginous joint and has slight flexibility. Cartilaginous joints also lack a joint cavity. The two types of cartilaginous joints are as follows

synovial membrane

inner layer of the articular capsule; made of loose connective tissue that lines the fibrous layer's internal portion and covers all internal surfaces of joints that are not covered with hyaline cartilage. manufactures synovial fluid.

Nonaxial movement

involves only slipping movements, because there is no axis around which the movement can take place.

arthritis

is a term that signifies more than 100 inflamma-tory or degenerative diseases, all of which damage the joints. Arthritis is the most common disease that results in crippling of movement in the United States, affecting one in five peo-ple. Acute arthritis usually develops from bacterial infec-tions, whereas chronic arthritis includes the forms known as osteoarthritis, rheumatoid arthritis, and gouty arthritis

subcutaneous prepatellar bursa

is an example of a bursa that is often injured by trauma to the anterior knee. The knee joint capsule is strengthened and stabilized by all three types of joint ligaments. Two of these types (cap-sular and extracapsular) help to prevent hyperextension of the knee. They are tightly stretched when the knee is extended. When the knee is extended, the extracapsular fibular and tibial collateral ligaments are crucial to prevent lateral or medial rotation.

gouty arthritis (aka gout)

is caused by accumulation of uric acid and primarily affects the joints of the great toe, but can also involve the joints of the fingers, wrists, knees, and ankles. It is much more common in men over the age of 30. Gouty arthritis is a condition based on excessive, abnormal levels of uric acid deposited as needle-like urate crystals in soft tissues of joints. An inflammatory response is triggered, and extremely painful gouty arthritis occurs. Usually, the joint at the base of the great toe is first affected. Men experience gouty arthritis much more than women because of their naturally higher blood levels of uric acid

multiaxial movement

is movement in or around all three planes of space and axes.

tibial collateral ligament

is wide and flat, running from the femur's medial epicon-dyle to the tibial shaft's medial condyle. This ligament is fused to the medial meniscus.

synarthrotic

joints are functionally classified as immovable aka fibrous joints

tendon sheaths

lengthened bursae wrapping totally around a tendon that is subjected to friction. They are common in areas such as the wrist, where several tendons are tightly crowded inside narrow canals.

fibrous joints

lying between bones that closely contact each other, fibrous joints are joined by thin, dense connective tissue. They have no actual joint cavity. An example of a fibrous joint is a suture between flat bones of the skull. No real movement takes place in most fibrous joints, making them synarthrotic in classification. Those with limited movement (amphiarthrotic) include the joint between the distal tibia and fibula. The amount of move-ment they have depends on the length of the connective tissue fibers that unite the bones. There are three types of fibrous joints:

biaxial movement

movement in two planes

Uniaxial movement

movement within one plane

joint capsules

outer layers of ligaments

Types of Synovial Joints

plane (gliding), hinge, pivot, ellipsoidal, saddle, and ball and socket.

The patella glides across the femurs distal end during knee flexion because the femoropatellar joint is a:

plane joint

menisci

shock-absorbing fibrocartilage pads

amphiarthrotic

slightly movable aka cartilingous

ischiofemoral ligament

spirals posteriorly. All three ligaments have an arrangement that causes a screw-like turning motion of the femur head into the acetabulum when a person stands up straight. They provide increased joint stability. reinforces the articular capsule of the hip with the iliofemoral ligament and the pubofemoral ligament.

Two strong capsular ligaments restrict horizontal movements:

the medial ulnar collateral ligament and the triangular radial collateral ligament on the lateral side.

shoulder joints

the shoulder joints are the most freely movable joints of the body, but they lack stability. They are ball-and-socket joints. The head of the humerus is large and hemispherical. It fits in the glenoid cavity of the scapula, which is shallow and small. This cavity is made slightly deeper by a fibrocartilage rim (the glenoid labrum). Still, it is only about one-third of the size of the humeral head, which means the shoulder joint is highly unstable.

coracohumeral ligament

the thickest area of the capsule. It helps to support the weight of the arm. The front of the capsule is only slightly strengthened by three glenohumeral ligaments. These are absent in some individuals.

sprain

there is stretching or tearing of the ligaments that reinforce a joint. The most commonly sprained joint ligaments are those of the ankle, knee, and lumbar spine. Sprains are usually painful and cause the immobilization of the injured patient. When partially torn, they heal very lowly because of a lack of vascularization. However, a complete ligament tear is treated with surgery, grafting, and long-term immobilization. Ends of ligaments can be sutured together, but this is difficult to perform because of the hundreds of fibrous strands involved in each ligament. Grafting is used instead for ligaments such as the anterior cruciate ligament. In this operation, part of a muscle tendon is attached to articulating bones. For other ligaments (such as the medial collateral ligament of the knee), long-term immobilization is as effective as surgical methods.

Symphyses:

type of cartilaginous joint: These are joints where fibrocartilage unites bones. Fibrocartilage acts as a shock absorber because of its ability to be com-pressed and then recover its original shape. A limited amount of movement at the joint is allowed. Hyaline cartilage is also present in symphyses, as articular cartilage on bony surfaces. Symphyses are amphiarthrotic joints allowing flexibility but maintaining strength. Examples include the pubic symphysis of the pelvis and the symphyses of the intervertebral joints.

Synchondroses:

type of cartilaginous joint: These are plates or bars of hyaline cartilage uniting the bones. Nearly all synchondroses are synarthrotic. In children, the best exam-ple of synchondroses are the epiphyseal plates in the long bones. These plates are temporary joints, eventually becoming synostoses. The immovable joint between the manubrium of the sternum and the first ribs costal cartilage is another example.

sutures

type of fibrous joint: Seams that occur only between the bones of the skull, sutures have waved and articulated bone edges that interlock. Each junction is totally filled by a tiny amount of extremely short connec-tive tissue fibers. These fibers are continuous with the periosteum, creating rigid structures joining the bones together. However, they also allow the skull to expand during childhood, when the brain is growing. Closed sutures, during brain growth, are better described as synostoses. The immobility of the sutures helps to protect the brain.

gomphoses

type of fibrous joint: These are fibrous joints with a peg-in-socket structure. In the human body, gomphoses are only exemplified by the articulation of the teeth in their alveolar sockets. The singular term gompho-sis refers to how the teeth are embedded in their socket (as if they were hammered in). In gompho-ses, the fibrous connects are the short periodontal ligaments.

Syndesmoses:

type of fibrous joint; Ligaments connect the bones in these joints, and the connecting fibers are longer than those found in sutures. The varied lengths of these fibers control the amount of movement that can occur. Syndesmoses with shorter fibers have lit-tle or no allowed "give" (movement): an example is the ligament connecting the distal ends of the fibula and tibia. When they are longer, more movement is possible: an example is the interosseous membrane (similar to a ligament) that connects the ulna and radius.

rotator cuff

which encircles the shoul-der joint. The rotator cuff blends with the articular capsule. If the arm is strongly circumducted, the rotator cuff can be stretched severely, which often occurs in athletes who pitch (such as those in baseball or softball).

ligamentum teres

which is the ligament of the femur head, is the flattened intracapsular band connecting the femur head to the acetabulums lower edge. During most movements of the hip, it is slack. It is not important in joint stabilization but contains an artery supplying the head of the femur. When the artery is damaged, severe hip joint arthritis may develop. Stability of the hip joint comes from the deep socket that strongly encloses the femur head, strong capsular ligaments, thick hip and thigh muscles surrounding it, and muscle tendons crossing it.